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膨润土与砂混合土中掺砂率的高低会引起混合土膨胀特性的差异。对纯膨润土及其低掺砂率混合土,浸水膨胀完成后蒙脱石孔隙比em与竖向应力σv在双对数坐标内呈唯一线性关系。对高掺砂率混合土,在较小荷载下浸水,不会形成砂骨架,em–σv线性关系仍成立;在较大荷载下浸水,会形成砂骨架,砂骨架形成后,em与σv间不再满足该线性关系。利用砂骨架孔隙比的概念可确定不同掺砂率混合土形成砂骨架时对应的起偏应力及混合土能够形成砂骨架的临界掺砂率。砂骨架形成前,砂颗粒被蒙脱石包围,外力由蒙脱石承担,最终变形量由试样中单位体积蒙脱石的含量决定。砂骨架形成后,竖向应力最终由砂骨架和蒙脱石共同承担,提出了确定不同掺砂率下两者承担比例的方法,进而可确定砂骨架形成后的膨胀变化量,预测结果与膨胀试验结果吻合较好。该方法可以预测高掺砂率混合土的浸水膨胀量。
The content of sand mixed with bentonite and sand will lead to the difference of swelling characteristics of mixed soil. For pure bentonite and its mixed soil with low content of sand, the porosity ratio of montmorillonite after immersion expansion is the only linear relationship in the double logarithm of vertical stress σv. For the mixed soil with high sand content, the sand framework does not form when the soil is soaked under low load, and the linear relationship of em-σv still holds. Under the condition of water flooding, the sand framework will be formed. After the sand framework is formed, No longer satisfy the linear relationship. The concept of porosity ratio of sand skeleton can be used to determine the corresponding deviatoric stress in the formation of sand skeleton with mixed sand mixed with different ratios of sand and the critical rate of sand mixed with sand to form sand skeleton. Before the sand skeleton is formed, the sand particles are surrounded by montmorillonite and the external force is assumed by the montmorillonite. The final deformation is determined by the content of montmorillonite per unit volume in the sample. After the formation of the sand skeleton, the vertical stress is finally shared by the sand skeleton and the montmorillonite. A method for determining the proportion of the two sand under different rates of sand incorporation is put forward to determine the variation of the expansion after the formation of the sand skeleton. The predicted results and expansion The test results agree well. This method can predict the infiltration expansion of mixed soil with high sand content.